Apparatus for isochoric gas compression

ABSTRACT

An apparatus for gas compression comprising:
         a container containing the gas to be compressed;   a first heat exchanger exchanging heat between a high temperature thermal source and the gas, to introduce heat into the gas;   a second heat exchanger exchanging heat between a low temperature thermal source and the gas, to extract heat from the gas;   supply means of the gas at a supply pressure and delivery means of the gas at a delivery pressure greater than the supply pressure);   gas permeable means configured to accumulate and transfer heat to the gas, and   gas permeable or gas impermeable movable means dividing the container into a first section in thermal communication with the first heat exchanger and in a second section in thermal communication with the second heat exchanger and in fluid communication with said supply means and said gas delivery means.

TECHNICAL BACKGROUND OF THE INVENTION 1. Field of the Invention

The present invention relates to an apparatus for isochoric gascompression, in particular to a gas for industrial use, which uses asdriving energy the thermal energy deriving from waste thermal flowspreferably from the same industrial plant. The apparatus according tothe invention substantially does not therefore require the need formechanical and/or electrical energy in order to carry out thecompression of the gas and consequently of a thermodynamic cycle which,starting from a thermal source, in this case waste thermal flows, makesthe aforementioned mechanical and/or electric energy available forcarrying out the compression.

2. Brief Description of the Prior Art

Many industries in which gas compression plants are used, have at theirdisposal large waste thermal flows the thermal energy of which generallycan be exploited for the production of electrical or mechanical energy.For this purpose, as is known, recovery organic Rankine cycle (ORC) orRankine cycle with water vapor, are used.

Compression plants need at the same time a driving energy and asubstantial portion of their energy needs is represented by thecompression of air or other gases.

According to the known art it is therefore possible to install arecovery cycle (with water vapor, gas or organic fluid), in order toproduce with it electric energy for actuating the compressors.

Another known technique is to couple the turbine of the recovery cycledirectly to the compressor by using the mechanical energy processed inthe turbine for the actuation of the compressor.

These solutions, although having high yields, require high installationcosts and involve the presence of rotating machines (turbines andcompressors) that require maintenance and can reduce the reliability ofthe system.

The Applicant has therefore recognized the need for developing anapparatus able to directly use the thermal energy for compressing a gas,without going through a thermodynamic cycle which turns the thermalenergy into mechanical and/or electric energy. In this way, an apparatusis obtained which, having a reasonable efficiency, requires lowinstallation and maintenance costs, thanks to its simplicity ofconstruction.

SUMMARY OF THE INVENTION

Purpose of the present invention is to provide an apparatus forisochoric compressing of gas, in particular of gas for industrial use,which uses almost exclusively thermal energy as driving energy derivingfrom waste thermal flows of the same industrial plant.

Traditionally, for compressing a gas using a thermal source, it isnecessary to install a recovery cycle, with which electrical ormechanical energy can be produced in order to actuate the compressors,as represented in a simplified way in FIG. 1. In FIG. 1, the heatexchanger 3′ uses the high temperature thermal source for preheating,vaporizing and possibly overheating a working fluid, for example anorganic fluid in an ORC. The vapor is then expanded into a turbine T,then it is condensed into a 4′ condenser; the liquid in the liquid stateis then compressed into a pump P by closing the cycle. The mechanicalenergy produced by the turbine T is used to actuate the electricgenerator G; the electric energy thus produced is used for actuating themotor M connected to the compressor (any difference between the electricenergy generated by G and that absorbed by M is supplied or absorbed bythe network to which G and M are electrically connected). The compressedgas can optionally be cooled with a 4″ exchanger. In otherconfigurations, the compressor can be directly coupled to the generator(the drive rotating train would in this case consist of turbine,generator and compressor), or directly to the turbine, instead of thegenerator.

Instead, the apparatus according to the present invention, althoughhaving a limited efficiency, does not require the use of the rotarymachines, if not for some auxiliary functions as will be seen below forsome embodiments, and therefore it allows low installation andmaintenance costs, thanks to its simplicity of construction.

According to the present invention, it is possible to compress the gasand return it up to a temperature close to the suction one, byexploiting a hot thermal source, a cold thermal source and a gaspermeable means, hereinafter also called regenerator, which is capableof accumulating and giving its heat to the gas.

According to the present invention an apparatus is described for theisochoric compression of gas, the characteristics of which are set outin the appended independent claim.

Further embodiments of the aforesaid preferred and/or particularlyadvantageous apparatus, are described according to the characteristicsset forth in the attached dependent claims.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will now be described with reference to the accompanyingdrawings, which illustrate some non-limiting embodiments thereof, inwhich:

FIG. 1 shows the scheme of a compression system with a recovery cycleaccording to known art,

FIG. 2 shows a scheme of an apparatus for the isochoric compression ofgas according to a first embodiment comprising a container, a heatexchanger which uses the hot source, a heat exchanger which uses thecold source and a regenerator gas;

FIG. 3 shows a second embodiment of the invention, described accordingto some equivalent variants;

FIG. 4 shows a third embodiment of the invention, described according tosome equivalent variants;

FIG. 5 provides details of the operation of the third embodiment of theinvention;

FIG. 6 shows a fourth embodiment of the invention with a furtherregenerator, placed in parallel with the exchanger using the hot thermalsource;

FIG. 7 shows the gas flows inside the isochoric compressor, according tothe fourth embodiment;

FIG. 8 and FIG. 9 show a fifth embodiment of the invention with furtherregenerators on both hot and cold sides, in parallel with thecorresponding heat exchangers;

FIGS. 10 A-G show various configurations of a sixth embodiment of theinvention;

FIG. 11 shows a seventh embodiment of the invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring now to the aforesaid Figures and in particular to FIG. 2, theprinciple of operation of the invention according to a first embodimentthereof is illustrated.

The apparatus 1 for isochoric gas compression comprises a container 2within which are positioned a first heat exchanger 3, preferably placedat the top, and a second heat exchanger 4, preferably placed at thebottom, respectively, in order to introduce heat into the system and toextract it. By way of example, the “hot” heat exchanger 3 could becrossed by a diathermal oil, whereas the “cold” heat exchanger 4 coulduse water cooled by a suitable circuit able to exchange heat with theenvironment. In the lower section 2 b of the container an inlet gas duct5 is present, which must be compressed and an outlet duct 6 for thecompressed gas, both being equipped with a corresponding supply valve V1and the discharge valve V2. The container 2 is traversed by a gaspermeable means, called regenerator 7, movable between a lower and anupper position and able to accumulate and transfer heat to the gas (forinstance, made with various overlapping metal mesh layers, whichexchange heat with the gas during the crossing of the same andaccumulate it within their mass). The regenerator 7 divides thecontainer 2 into two sections, an upper section 2 a, at a highertemperature, and a lower section 2 b, at a lower temperature. Thevolumes of the two sections 2 a and 2 b are obviously variable accordingto the position of the regenerator 7. The pressures in the two sectionsare instead approximately the same, being the gas permeable septum.

Referring to the positions of the regenerator 1A to 1E, to theconfigurations of the valves V1, V2 (0=closed, 1=open) and to thecorresponding graphs which, according to the aforementioned positions ofthe regenerator, respectively represent the regenerator stroke and thegas pressure, the apparatus) works according to the following logic:

-   -   position 1A: the regenerator 7, with the thermal storage mass at        a temperature close to T1, is placed in the upper portion of the        container, in correspondence of the first heat exchanger 3 and        without the dead volume occupied by the heat exchanger itself;        the pressure in the entire container 2 is close to the inlet        pressure Pin. Almost all gas present in the apparatus has an        inlet temperature T0, except for which remaining inside the dead        volume at the top and a portion of the gas remaining inside the        regenerator matrix, at a temperature between T1 and T0;    -   the regenerator 7 moves downwards due to an actuator (of the        known type and not shown in FIG. 1) which does not perform any        mechanical work other than that necessary to overcome the fluid        dynamic and mechanical frictions; the regenerator when moving        downwards, is crossed by a certain flow of gas and heats the        same, due to the previously accumulated heat. The gas also        receives a heat Qin from the “hot” heat exchanger 3. In this        stage, the valves V1, V2 are closed and a gas is heated in a        closed volume, the pressure increases, both in the (hot) portion        at the top of the regenerator and in the one (cold) at the        bottom of the same, which has a fluid connection with the upper        one through the “permeable” matrix of the regenerator;    -   in position 1B, the gas has reached the desired pressure,        therefore the valve V2 opens, causing a certain flow of gas to        pass to an environment placed at a pressure Pout.

It must be considered that in the hypothesis of a perfect gas, themaximum obtainable pressure is derived from the law of gases P*V=M*R*Twhich, once applied to the specific case (To and T1, V constant, Rconstant, M constant) permits to obtain Pout_(max)=Pin*T1/T0. The valveV2 is actuated at a pressure lower than this maximum pressure, as bythis Pout_(max) a useful outlet flow rate would not be associated (infact, in the applied gas relation, the volume must be constant). Thecloser is Pout with respect to Pin (that is, the lower is the requiredcompression ratio), the greater the extractable flow rate for each cycleof the system (at the expense of an obviously moderate Pout/Pincompression ratio).

The system delivers a pressurized gas until the regenerator has reachedthe lower dead point (position 1C). The supplied gas has approximatelythe temperature T0, due to the fact that it passes through theregenerator before passing through V2 and in the presence of the “cold”heat exchanger 4 placed in the lower portion of the container;

-   -   in position 1C (regenerator in the lower position) the valve V2        closes as the system is no longer able to supply gas at the        required pressure;    -   the regenerator 7 moves upwards (position 1D) and during this        movement cools the gas passing through it (that is, the        regenerator heats up). The combined effect of the passage        through the regenerator and the transfer of heat towards the        “cold” exchanger reduces the pressure, until opening the valve        V1 and thus allowing the reintegration of a new gas. The gas        inlet continues until the regenerator 7 has reached the upper        dead point (position 1E).

The beginning or the end of some phases may not coincide with the upperand lower dead points, as the pressure inside the apparatus, in acertain instant, also depends on the heat input supplied by theexchangers 3 and 4, and not only on the position of the regenerator 7.

In this way it is therefore possible to return the compressed gas to atemperature close to the suction one, by simply exploiting a hot thermalsource, a cold thermal source and a gas regenerator, without the needfor the addition of other energy as well as a thermal energy, apart fromthe small fraction needed to cyclically actuate the regenerator insidethe container. Preferably, the regenerator 7 performs a complete cyclein a time ranging from 1 to 10 seconds, for example in relation to acontainer volume 2 of about 1000 liters and a height of about 1 m.

An alternative embodiment of the invention is shown in FIG. 3. Thisembodiment provides that the regenerator 7 a is external to container 2.In particular, in the configuration 3A, the regenerator 7 a is externalto the container 2 and is fixed, whereas a disc or septum 8 impermeableto gases move within the container; the movement of this movable means 8is allowed by an outer actuator (not shown in the Figure) and causes thegas to move from the lower section 2 b to the upper one 2 a or viceversa, by passing through the regenerator 7 a which is in fluid-dynamicconnection with both sections of the container 2.

The configuration 3B is similar to the previous one, but instead ofmoving the disc with a mechanical actuator, the gas is moved by one ormore fans 9 capable of generating a reversible flow. The disc is made aslight as possible and moves accordingly in order to equalize thepressures between the two sections 2 a and 2 b of the container.

In the configuration 3C also the first heat exchanger 3 and the secondheat exchanger 4 are placed outside the container. Obviously, in FIG. 3possible combinations are shown between the various ones.

A third embodiment of the invention is shown in FIG. 4.

In particular, in FIG. 4A the heat exchangers 3, 4 and the regenerator 7are placed outside the container. Two recirculation ducts R1, R2 arealso present with corresponding fans, in order to uniform thetemperature within the two sections 2 a and 2 b of the container. Thedisc 8 is actuated by suitable not shown actuators.

The configuration in FIG. 4 B differs from the previous one only for thepositioning of the heat exchangers 3, 4 which in this case are housedwithin the container 2.

The operating logic of the configuration of FIG. 4A or 4B is illustratedwith reference to the subsequent FIG. 5.

When the disc 8 moves downwards, that is towards the cold source (FIG.5A), the cold gas contained in the lower section 2 b crosses the duct R1with a flow equal to the sum of the mass flow m1 corresponding to themovement of the disc 8 within the container 2 (when there is noexpulsion or introduction of gas through the valves V1 and V2) and ofthe flow rate m2 recycled by the fan. The “cold” heat exchanger 4 iscrossed by a gas flow rate equal to m2, whereas the regenerator 7 a iscrossed only by the flow rate m1 corresponding to the movement of thedisc 8 within the container 2.

During the movement downwards of the disc 8, the gas passes through theregenerator, heating up and then through the fan 9 a and the “hot” heatexchanger 3″. In the heat exchanger 3 passes a flow rate equal to m1+m3,thanks to the flow rate provided by the fan. The flow rate m1 which hasleft the section 2 b of the container is equal to the flow rate thatenters the upper section 2 a of the container (subtracted the amountscumulated in the volumes of the respective components), whereas theremaining flow rate m3 cannot but be recycled upstream of the fan forthe recirculation duct R2.

When the disc moves upwards towards the hot source (FIG. 5B), theregenerator 7 a is always crossed by the flow rate m1, but in theopposite direction. The hot gas contained in the lower section 2 apasses through the recirculation duct R2 with a flow rate equal to thesum of the flow rate m1 corresponding to the movement of the disc 8 inthe container 2 and of the flow rate m3 recycled by the correspondingfan. The “hot” heat exchanger 3 is crossed by a gas flow rate equal tom3, whereas the regenerator 7 a is crossed only by the flow rate m1corresponding to the movement of the disc 8 in the container 2.

The gas then passes through the regenerator, cooling down and thenthrough the fan 9 b and the “cold” heat exchanger 4. In the heatexchanger 4 passes a flow rate equal to m1+m2, thanks to the flow rateprovided by the fan. The flow rate m1 which has left the section 2 a ofthe container is equal to the flow rate entering the lower section 2 bof the container, whereas the remaining flow rate m2 cannot help but berecycled upstream of the fan for the recirculation duct R1.

The flow rates involved are established by the prevalence of the fanwith respect to the load losses of the respective branches. More indetail, it is sufficient to increase the rotation speed of the fan 9 aof the hot branch with respect to the rotation speed of the fan 9 b ofthe cold branch, in order to obtain a lowering of the pressure at thenode K with respect to the node H and therefore a flow from H to K andvice versa. In this way an alternating flow is obtained without usingvalves.

The gas enters or leaves the system through the valves V1 and V2 when,respectively, the pressure in the lower portion of the exchanger dropsbelow the inlet pressure or rises above the outlet pressure, with thelogic already described for the configuration in FIG. 2.

FIG. 6 shows a further possible configuration, in which the upper “hot”branch has a further gas permeable means, the regenerator 7 b, placed inparallel with the “hot” heat exchanger 3.

In previous solutions, the regenerator 7, 7 a supplies a great portionof the heat required to bring the gas to a higher temperature, and the“hot” heat exchanger 3 supplies the remaining heat portion. Therefore,in the heat exchanger 3, the heat exchange occurs with the gas beingalready at high temperature, as the gas has been already heated by theregenerator. Therefore also the heat carrier, for example diathermicoil, which flows into the heat exchanger 3 works with relatively lowtemperature differences. This phenomenon may adversely affect theability to perform an effective heat recovery from a gaseous effluent asa low temperature difference of oil affects the ability to effectivelycool down the gaseous source, just because the oil remains at relativelyhigh temperatures.

In the configuration of FIG. 5, the central regenerator 7 c which iscrossed by the entire gas flow, has a smaller size compared to those ofthe previous configurations and therefore its recovery is lower. This iscompensated by the presence of the second regenerator 7 b, in parallelto the heat exchanger 3. In this way, the gas which moves upwards andoutwards of the central regenerator 7 c will exit at the node ‘X’ at alower temperature (with respect to the case of a single generator 7 c).One portion of the gas is then heated by the second regenerator 7 b andanother portion is parallel heated by the heat exchanger 3 incounter-flow with the diathermic oil. In this way the introduction ofheat from the diathermic oil takes place at a variable temperature andstarting from a temperature at the lower node ‘X’, has a greatereffectiveness then regarding the recovery of the gaseous source for whathas been said previously. In the circuit there is present a non-returnvalve 100 which allows the gas to cross both the regenerator 7 b and theexchanger 3 when the flow is substantially directed upwards (that is,when the septum within the container moves downwards) but permits tocross only the regenerator 7 b when the flow is directed downwards (thatis, when the septum within the container moves upwards).

In fact, when the flow is directed downwards it would becounterproductive to let the hot gas flow through the exchanger 3 whichhas the function of giving heat and not of absorbing it. On the otherhand, the giving of heat from the heat exchanger 3 to the gas is notcontinuous, but takes place only for a half-cycle of operation, or inany case in an uneven manner.

FIG. 6B shows a similar solution, in which the exchangers 3 and 4 andthe regenerator 7 b are placed within the container 2, in order tominimize the dead volumes, that is the spaces occupied by the compressedgas which the system cannot expel. The exchanger 3 is placed in parallelwith the regenerator 7 b; for example, and the exchanger 3 develops on acircular crown inside which there is the regenerator 7 b. The gas flowdirected upwards in the heat exchanger 3 is prevented by one or morenon-return valves 100, for example of the clapet type.

In FIG. 7 the gas flows within the isochoric compression apparatus areshown, depending on the movement of the disc 8 placed in the container.If the disc moves downwards, the “cold” heat exchanger 4 is crossed by aflow rate m1+m2, of which m2 is the flow rate recycled by the lower fan9 c. The gas then goes up the central regenerator 7 c, heating up with aflow rate m1, generated by the central fan 9, which can generate a flowin both directions. Then the gas is divided between the “hot” heatexchanger 3 and the second regenerator 7 b arriving in the upper section2 a of the container.

Another possible configuration with regenerators in parallel with theheat exchangers is shown in FIGS. 8 and 9, in which the upper “hot”branch has a further gas permeable means (the regenerator 7 b), placedin parallel with the “hot” heat exchanger 3 and the “cold” lower branchhas a further gas-permeable means (the regenerator 7 d), placed inparallel to the “cold” heat exchanger 4. The operating logic correspondsto that already described for FIGS. 5A and 5B, with the addition of twofurther regenerators 7 b and 7 d placed on the recirculation branch andin parallel with the “hot” and “cold” exchangers.

FIG. 9 shows a possible arrangement of the regenerators and the fansaccording to the diagram of FIG. 8. The fans are preferably of axial orcentrifugal type and receive at their inlet the outgoing gas from thecentral regenerator 7 c and the second hot regenerator 7 b, arrangedaround the inlet duct of the fan 9 a. The flow rate expelled by the fan9 a passes the hot exchanger 3 and arrives inside the container 2. Thesame arrangement is adopted for the cold side.

FIG. 10A shows a further configuration, in which the septum 8 separatingthe hot and the cold environment within the container does not translatebut rotates around an axis o-o. Its operation is exactly equal to thatdescribed for the configuration of FIG. 2. When turning the septumclockwise, this causes the gas to move from the cold to the hot side, bypassing through the regenerator 7 e. Preferably the septum will becharacterized by a peripheral speed (at the point furthest from the axiso-o, and therefore with a greater speed), mediated on a complete workingcycle (therefore with return to the initial position) included in therange between 1 and 7 m/s.

For the lower values of average peripheral velocity, a law of motionwill be chosen which foresees the length of angular acceleration anddeceleration concentrated towards the beginning and the end of thedisplacement (in order to minimize the load losses).

For higher average speeds, the motion will preferably be close to asinusoidal motion, in order to minimize the forces of inertia generatedby the motion. The hot source is distributed in the exchange pipes (oris collected by them) through suitable collectors 11; the cold source iseither distributed or collected by the collectors 12. Duct 5 and duct 6are respectively the inlet and outlet ducts of the gas to be compressed.

The configuration of FIG. 10B is similar, except that the manifoldssupplying the heat exchange tubes are arranged along the axis of thecontainer 2, so that the manifolds 11, 12 and the pipes are fixed to oneof the bases of the container. In this way the heat exchangers 3, 4 and7 and the regenerator can be easily extracted in the axial direction.

FIG. 10C shows a further configuration for the system characterized by arotating septum around an axis. The configuration is characterized inthat the exchanger with the hot source 3 extends for a fraction x of thepassage surface available upon crossing the gas pushed by the septumduring its rotation about the axis o-o. The 1-x fraction is insteaddedicated to a further matrix 7 e′ with characteristics suitable for useas a regenerator. The fluid within the matrix can be channeled in asubstantially tangential direction, thanks to the presence ofnon-permeable or low permeable walls NP. In a completely similar manner,as shown in FIG. 10D, a portion y of the access surface can be dedicatedto a further regenerator 7 e″. Also, in this case, the non-permeablewalls NP can benefit the correct flow orientation. Moreover, in FIG. 10Dthe manifolds are arranged within the container 2. FIG. 10E shows asection of the previous Figure, in which the manifolds 11-12 areevidenced which protrude through the base flange FB, so as to allow aneasy removal of the dome of container 2 for maintenance of internalcomponents, in particular regenerators and heat exchangers, with the hotand cold sources.

In FIG. 10F a solution is shown with the heat exchange elements (heatexchangers with the sources and regenerators) which are reproduced in amirror-like manner, and with a double septum 8 and 8′. The advantage ofthis configuration is to allow a better balance of the rotating masses,with the consequent possibility of strongly increasing the oscillationspeed of the septum, and therefore of increasing the production ofcompressed gas.

In a further version of the proposed scheme, the mobile septum 8 is alsomade by an exchange matrix adapted to constitute a regenerator. In thiscase the flow rate passing through the exchangers 3 and 4 respectivelyand the matrices of the adjacent regenerators is pushed through saidcomponents as a consequence of the load loss which is generated duringthe motion of the septum. For better clarification, the flow rates aredivided between the rotating septum and the fixed exchange components inrelation to the pressure loss generated by the flow passing throughthem.

In FIG. 10G some possible details are added, such as brush seals SP,between septum and dome. The regenerator can be made with differentcompactness, in order to distribute the load losses and therefore theflow rate in a different way between 7 e and 7 e′. An eventuallyunidirectional valve VNR promotes the motion of the gas in a certaindirection, for example by limiting its passage through the hot exchanger3 during the gas cooling phase.

In a further embodiment of the present invention, as shown in FIG. 11, avolume is present with a front surface which is helically increased. Therotating septum and the exchangers/regenerators are helically shaped.The heat exchange elements 3, 4, the gas permeable means 7 e are fixedeither to the base flange or to the walls of the tank and havenon-permeable walls NP and brush-like seals SP connected to the rotatinghub. The helical septa 8 are fixed to the rotating hub. The elementsjust described are clearly visible in the enlargement of FIG. 11: thevolume occupied by the tubes of the hot source is indicated with 3, thevolume occupied by the tubes of the cold source is indicated with 4 andthe regenerator is indicated by 7 e.

This embodiment has peculiar characteristics and consequent advantages.The helical arrangement releases the frontal area of the exchangers fromthe sectional surface of the container. For example, in the rotatingconfiguration with flat heat exchangers/regenerators, the section of thelatter can only equal to that of the cylinder. The advantage of thehelical arrangement is to permit to greatly increase the frontal area ofthe exchange matrices, substantially by disengaging it from the area ofthe axial section of the container.

Moreover, the conical shape gives the system a certain elasticity inorder to cope with differential thermal expansions and with the internalpressure.

This solution makes it possible to vary, during the project, the passagesurface by varying the number of threads (in the direction of windings)or the angle α.

Further advantages consist in that the masses are roughly balancedaround the axis and that the cone resists to the pressure better than aflat surface.

In all the embodiments of the invention, the regenerator must be able toaccumulate a relatively large portion of the heat exchanged in thedifferent phases, therefore it must have an adequate overall mass. Inorder to limit the overall dimensions and optimize the heat exchange,the regenerator for example can be realized as follows:

-   -   a porous matrix;    -   a set of small diameter wires or tapes which are welded or        crushed with each other and are externally crossed by the gas;    -   metal wire meshes or other material suitable for the        temperatures of the cycle (that is, ceramics meshes), which are        tightly and overlapping arranged.

The present invention, in every one of its possible configurations, canin theory operate with any difference in temperature between the hot andcold source; obviously, the higher the temperature of the hot source andthe greater the difference in temperature with the cold source, thebetter are the performances, in terms of efficiency and compressionratio. Regarding the cold source, this could be made of a water-cooledcircuit with air cooler, therefore with water temperatures typicallyranging from 10° C. to 50° C. depending on the year season and itslocation. The hot source could be made of waste fumes coming from anindustrial process or from the exhaust of an internal combustion engineor gas turbine, therefore with temperatures typically ranging between200° C. and 800° C.; however, as the gas/gas heat exchangers need largeexchange surfaces, it is more convenient to realize the presentapparatus in such a way, that an intermediate heat exchange circuit isformed between waste fumes and gas to be compressed (that is, diathermicoil or molten salt). The Author considers therefore convenient torealize the present invention so that the “hot” exchanger 3 receives atits inlet a carrier fluid at a temperature ranging between 200° C. and450° C., as such temperatures are sufficiently high to obtain goodcompression ratios, but, at the same time, remain below the limits ofuse of the common diathermic oils present on the market.

Within these limits of temperature, the highest compression ratiosattainable (Pout/Pin) are roughly comprised between 1.1 and 2.5. Theseare maximum values being achieved in a closed system, that is withoutentry or exit of gas (therefore with zero efficiency); the extraction ofcompressed gas leads to the achievement of lower pressures with respectto the limits set out above: the greater the required flow rate, thelower the pressure reached. According to the Author, a good compromisebetween discharge pressure and flow rate is obtained for compressionratios ranging between 1, 1 and 2.

The present invention therefore allows to have relatively lowcompression ratios, for example close to 1.3.

It is therefore particularly useful that the inlet pressure is alreadyhigh, for example equal to 3 MPa, as with a ratio of 1.3, pressuresclose to 4 MPa can be achieved.

It is also evident that higher values of compression ratio can beachieved by arranging in series a greater number of apparatusesaccording to the present invention.

Due to the fact that the apparatus outputs compressed gas in anon-continuous way, the energy is related to the speed of displacementof the separation septum or regenerator (depending on the configurationconsidered). The Author believes that the system can preferably operatewith a cycle time of between 1 and 10 seconds, for example in relationto a volume of container 2 of about 1000 liters and with a height ofabout 1 m. These time values consider inertias of the separation septum,thermal energies reasonably achievable from the exchangers and theregenerator, energies of fans and therefore load losses.

In addition to the embodiment of the invention, as described above, itis to be understood that numerous further variants exist. It must alsobe understood that such embodiments are only exemplary and limit neitherthe scope of the invention, nor its applications, nor its possibleconfigurations. On the contrary, although the above description makes itpossible for the skilled technician to implement the present inventionat least according to an exemplary embodiment thereof, it must beunderstood that many variations of the described components areconceivable, without thereby departing from the scope of the invention,as defined in the attached claims, which are interpreted literallyand/or according to their legal equivalents.

1. An apparatus (1) for gas compression comprising: a container (2)containing the gas to be compressed; a first heat exchanger (3)exchanging heat between a high temperature thermal source and the gas,to introduce heat into the gas; a second heat exchanger (4) exchangingheat between a low temperature thermal source and the gas to extractheat from the gas; supply means (5) of the gas to a supply pressure(Pin) and delivery means (6) of the gas at a delivery pressure (Pout)greater than the supply pressure (Pin); gas permeable means (7, 7 a, 7b, 7 c, 7 d, 7 e, 7 e′, 7 e″) configured to accumulate and transfer heatto the gas, and gas permeable (7) or gas impermeable (8) movable meansdividing the container (2) into a first section (2 a) in heatcommunication with the first heat exchanger (3) and in a second section(2 b) in thermal communication with the second heat exchanger (4) and influid communication with said supply means (5) and said gas deliverymeans (6); the apparatus (1) being characterized in that said first heatexchanger (3) and second heat exchanger (4), said gas permeable means(7, 7 a, 7 b, 7 c, 7 d, 7 e, 7 e′, 7 e″) and said movable means (7, 8)cooperate to heat and cool the gas, causing it to cyclically flowbetween the first section (2 a) and the second section (2 b), to obtainthe compression effect of the gas, which is introduced into thecontainer, from a value equal to the supply pressure (Pin) up to a valueequal to the discharge pressure (Pout).
 2. The apparatus according toclaim 1, wherein said gas permeable means (7, 7 e, 7 e′, 7 e″) areinternal to the container (2).
 3. The apparatus according to claim 1,wherein said gas-permeable means (7 a) are external to the container (2)and in fluid-dynamic communication with both the sections (2 a, 2 b) ofthe container.
 4. The apparatus according to claim 1, wherein said firstheat exchanger (3) and the second heat exchanger (4) are internal to thecontainer (2).
 5. The apparatus according to one of claim 1 wherein saidfirst heat exchanger (3) and the second heat exchanger (4) are outsidethe container (2).
 6. The apparatus according to claim 1, furthercomprising at least one fan (9) which moves said movable means (7, 8).7. The apparatus according to claim 1, further comprising at least onerecirculating duct (R1, R2) provided with a correspondent fan (9 a, 9 b,9 c).
 8. The apparatus according to claim 1, further comprising anadditional gas permeable means (7 b), which is allocatedfluid-dynamically in parallel with respect to the first heat exchanger(3).
 9. The apparatus according to claim 1, further comprising anadditional gas permeable means (7 d), which is allocatedfluid-dynamically in parallel with respect to the second heat exchanger(4).
 10. The apparatus according to claim 1, wherein said container (2)has a shape corresponding to a solid of rotation and said movable means(8) rotates inside the container (2).
 11. The apparatus according toclaim 1, wherein said container (2) contains heat exchange tubes,arranged inside and parallel to its axis.
 12. The apparatus according toclaim 1, wherein said first exchanger (3) extends for a first fraction(x) of the passage surface crossed by the gases and a second fraction(1-x) comprises an additional gas permeable means (7 e′).
 13. Theapparatus according to claim 1, wherein said second exchanger (4)extends for a first fraction (y) of the passage surface crossed by thegases and a second fraction (1-y) comprises a further gas permeablemeans (7 e′″).
 14. The apparatus according to claim 10, furthercomprising at least two collectors (11, 12) extending through a baseflange (FB) to allow easy removal of the cap of the container (2). 15.The apparatus according to claim 10, further comprising a double movablemeans (8, 8′) which is impermeable to the gases and heat exchangers (3,4) symmetrical to each other and gas permeable means (7 e) symmetricalbetween them.
 16. The apparatus according to claim 1, further comprisinga one-way valve (VNR, 100) which hinders to passage of the gas in thefirst heat exchanger (3) during the gas cooling phase, at a greaterdegree than during the gas heating phase.
 17. The apparatus according toclaim 10, in that it comprising an exchange volume having a frontsurface, wherein rotating movable means (8), heat exchangers (3, 4), andgas permeable means (7 e), are helical shaped.
 18. The apparatusaccording to claim 17, wherein said heat exchangers (3, 4) and the gaspermeable means (7 e) are fixed to a base flange or to the cap, whilethe helical movable means (8) are fixed to a rotating hub.
 19. Theapparatus according to claim 1, having an average peripheral velocity atthe farthest point from the axis, between 1 and 7 m/s.
 20. The apparatusaccording to claim 1, wherein said gas permeable means (7, 7 a, 7 b, 7c, 7 d, 7 e, 7 e′, 7 e″) comprise a porous matrix or a set of wires orstrips or even dense metal meshes, said elements being welded or pressedtogether and externally crossed by the gas.
 21. The apparatus accordingto claim 1, wherein said first heat exchanger (3) is supplied with acarrier fluid having an inlet temperature between 200° C. and 450° C.